This invention relates to anti-theft systems and more particularly to anti-theft systems used with supermarket shopping carts.
Supermarket shopping carts and similar carts used by other retail and commericial organizations are often quite expensive because they must withstand constant strenuous use and, consequently, must be constructed of the relatively expensive materials which are able to withstand such use. Such carts are often stolen or carried away and abandoned. Consequently, the cost of providing these expensive carts has become a significant part of the overhead of a number of businesses. For this reason, many anti-theft devices have been suggested for use with such carts.
For example, U.S. Pat. No. 4,242,668 to Herzog discloses a shopping cart theft prevention system which includes a transmitter and a receiver carried by the cart. When the cart is taken beyond a predetermined distance from its place of use, a signal from the transmitter disables the cart by causing the front set of wheels to be retracted upwardly so that the front portion of the cart drags on the ground. Such a system requires that the carts be designed or modified for use with the particular system. Modification of carts presently in use would be very expensive.
U.S. Pat. No. 2,964,140 to Berezny discloses another anti-theft system for shopping carts in which magnetic material is embedded in the pavement surrounding the facility with which carts are to be used, and an arrangement which is responsive to magnetic field variations is provided for locking the wheels of the cart when the cart is removed from the area. Again, the system requires a substantial investment in changes to the existing carts and in the installation of pavement containing magnetic material. U.S. Pat. No. 3,495,688 to Isaacks shows another arrangement utilizing carts with magnetically actuated locking wheels.
Each of these systems provides a solution to the problem, and each of these systems is quite expensive to implement. Some of these systems are so expensive that the economics of providing such a system outweigh the advantages provided thereby. Each of the systems requires that modifications be made to the carts themselves. Certain of these systems can only be used with specifically designed carts and, consequently, cannot be used with the large variety of carts presently in use. Known systems which utilize receiver-transmitter arrangements have proven to be quite expensive in use and require constant replacement of batteries utilized in the receivers.
It is, therefore, an object of this invention to provide an improved anti-theft device for shopping and similar carts which device may be utilized on a great variety of different carts without modification of the carts.
It is another object of this invention to provide an electronic system with extremely low power requirements for preventing theft of shopping carts.